GMC fuel pump

This Fuel pump is a 2 valve model off a CCKW352, but may well have been fitted to many different vehicles, it is made by AC.

To remove the fuel pump there are the 2 fuel lines ( remember to turn off the fuel tap !!!! ) 2 fixing bolts which need to be removed, the fixing bolt nearest to the front is hollow which has the oil line from the bottom of the oil filter screwed into it as seen below.

To remove this oil line you need to hold the nut part nearest the hose to prevent it from turning and then turn the other nut nearest the end, do this at both ends then remove oil line from each fitting ( NOTE you wont get covered in oil when the bottom hose is removed )

You can then undo both bolts and remove the fuel pump.

Here is the pump split in half without the diaphragm and the top filter bowel removed

Here is the top part of the fuel pump with bowel on but with bowel clamp removed

Here is the top part with the bowel removed

This is the underside showing the two valves

This is the new diaphragm and spring

This is up the wrong way up in relation to the mounted position of the fuel pump but you can now see the rectangular hole in the shaft of the diaphragm this has to hook under the opperating lever in the base part of the fuel pump body as in the pic below

Once this is done then you can reassemble the fuel pump and as they say the fitting is the reverse of the removal.

An interesting thing I have found is that in the base part of the fuel pump there is a raised lip this I think is to stop fuel if the diaphragm splits from getting in to the engine and diluting the oil

This lip coupled with the washers and leather seals on the diaphragm shaft

Helps to seal the route to the engine also in the top pic at 12 o'clock there is a hole by the fuel priming lever and this I believe is a weep hole to allow any fuel to escape and indicate there is a problem with the diaphragm rather than just pouring into the engine..